/*
 * @Author: Clark
 * @Email: haixuanwoTxh@gmail.com
 * @Date: 2023-01-13 16:53:10
 * @LastEditors: Clark
 * @LastEditTime: 2023-01-28 09:20:27
 * @Description: file content
 */

#include "apue.h"
static void sig_int(int);

int main()
{
    sigset_t newmask, oldmask, waitmask;

    pr_mask("program start: ");

    if (signal(SIGINT, sig_int) == SIG_ERR)
    {
        err_sys("signal(SIGINT) error");
    }

    sigemptyset(&waitmask);
    sigaddset(&waitmask, SIGUSR1);
    sigemptyset(&newmask);
    sigaddset(&newmask, SIGINT);

    // block SIGINT and save current signal mask
    if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
    {
        err_sys("SIG_BLOCK error");
    }

    // critical region of code
    pr_mask("in critical region: ");

    // pause, allowing all signals except SIGUSR1
    if (sigsuspend(&waitmask) != -1)
    {
        err_sys("sigsuspend error");
    }
    pr_mask("after return from sigsuspend: ");

    // Reset signal mask which unblocks SIGINT
    if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
        err_sys("SIG_SETMASK error");

    // And continue processing ...
    pr_mask("program exit: ");

    exit(0);
}

static void sig_int(int signo)
{
    pr_mask("\nin sig_int: ");
}
